Tubular heat exchanger with thermostatic valve



Jan. 7, 1969 R. L. CAMPBELL 3,420,293

TUBULAR HEAT EXCHANGER WITH THERMOSTATIC VALVE Filed May 4, 1967 HIS AOR/VEY MN NN United States Patent O 3,420,293 TUBULAR HEAT EXCHANGERWlTH THERMOSTATIC VALVE Robert L. Campbell, Dayton, Ohio, assignor toUnited Aircraft Products, Inc., Dayton, ho, a corporation of Ohio FiledMay 4, 1967, Ser. No. 636,187 U.S. Cl. 165-39 Int. Cl. F285. 27/00 9Claims ABSTRACT F THE DISCLGSURE This invention relates to tubular heatexchangers, and particularly to a generally new construction and mode ofoperation of devices of that class wherein a control valve assembly isdisposed in the core of the heat exchanger and extends through one endthereof to control flow of the tube side iluid.

An object of the invention is to provide a heat exchanger as describedof a more compact form than were the control valve assembly to beexternally located, as is conventional.

Another object of the invention is to provide a relationship of partssuch that the control valve assembly is more sensitive to a sensedcondition to achieve a stabilized temperature control.

A further object of the invention is to provide a. heat exchanger wellconstructed for growth in heat transfer capability without increasingthe size of the heat exchanger itself.

Still another object of the invention is to provide a construction asdescribed lending itself to ease of assembly and which is essentiallytrouble free in operation.

Other objects and structural details of the invention will more clearlyappear from the following description, when read in connection with theaccompanying drawings, wherein:

FIG. l is a view in longitudinal section of a tubular heat exchanger inaccordance with the illustrated embodiment of the invention;

FIG. 2 is a view in cross section, taken substantially along the line2-2 of FIG. l; and

FIG. 3 is a `fragmentary detail view of an alternate form of valvecontrol.

Referring to the drawings, a tubular heat exchanger in accordance withthe illustrated embodiment of the invention comprises an elongatedtubular shell open at its opposite ends. Near such ends are respectiveheader plates 11 and 12. These are tube sheets, accommodating theopposite ends of heat transfer tubes 13 in through holes drilled orotherwise formed in the plates. The tubes 13 extend between andinterconnect the plates 11 and 12 and have a thin walled metallicconstruction for an eflicient conducting of heat through the wallsthereof.

The opposite ends of the tubes 13 open through and beyond the respectiveheader plates 11 and 12.

At one end of the shell 10 is an adapted ring 14 to which is bolted orotherwise secured a closure cap 15. A metallic O-ring 16 or the like isinstalled between cap and adapter ring 14 to seal against escape ofpressure fluid from a chamber 17 formed between cap 15 and the adjacentheader plate 11. The cap 15 has a central portion defining a pad 18parallel to the header plate 11. On the inner surface of pad 18 is arecessed surface 19 machined to provide a flat valve seat. In the centerof seat 19 is a longitudinal through opening 21 in pad 18 positioned tobe concentric with shell 10 and header plate 11. Projecting from theouter surface of pad 18 is a boss 22 formed for connection with a fluidflowing conduit and having a central bore 23 communicating throughopening 21 with what may be considered an end chamber 17.

At the opposite end of shell 10 a similar end chamber 2.4 is formedthrough the cooperation of an adapter ring 25 and a closure cap 26. Inthis instance, cap 26 has a rearwardly projecting boss 27 for connectionin fluid flowing conduit. It has further an inwardly projectingcylindrical portion 28 terminating in an expanded flange 29 received ina sleeve 31 installed in a central opening 32 in header plate 12.Inwardly and outwardly projecting portions of the cap 26 have a commonbore 33 opening through outer boss 27 and terminating in a vertical wall34 from which expanded flange 29 projects. Radial openings 35communicate bore 33 with end chamber 24.

The above described construction and arrangement of parts is one inwhich a tube side -uid may enter shell 10 at one end, distribute itselfin an end chamber and flow longitudinally through the tubes 13 to theother end chamber and out of the shell. The shell 10 has openings 36 and37 between the header plates 11 and 12 and respectively adjacent suchplates. A shell side lfluid enters the shell by one of these openings,flows over and around the tubes 13 and leaves by way of the otheropening. The tube side fluid and shell side fluid accordingly are inheat transfer relation to one another through the walls of tubes 13 and,in accordance with the general mode of operation of devices of thisclass, the iluid of higher temperature yields up some of its heat to thefluid of lower temperature. More effective heat transfer takes place ifthe shell side fluid is not permitted to flow directly between theopenings 36 and 37 but rather is required to flow circuitously throughthe shell 10` making a number of generally cross flow passes across thetubes 13. To this end, longitudinally spaced apart batlles 3-8, 39 and41 are disposed in shell 10 in transverse relation to the tubes 13. Thebaffles 38, 39 and 41 have a height corresponding approximately tothree-fourths the internal diameter of shell 10. Seated to the shellinterior on one side thereof the batlles accordingly provide a flow areabetween their outer ends and the opposite side of the shell. Arranged inan alternating order as illustrated, the baffles compel cross flow ofthe ilowing shell side fluid in s-uccessive passes as described. In theillustrated instance the opening 36 serves as the inlet for the shellside fluid while opening 37 is the outlet. Shell side tluid enters theshell at opening 36, is constrained by baille 38 to ilo-w across thebundle of tubes 13 to the opposite of the shell. There it is allowed topass over the outer free end of baflle 33 and as compelled and directedby subsequently encountered baffles 39 and 41 makes successive passesacross the tube bundle, the nal pass flowing the fluid transverselybetween baffle 41 and header plate 12 toward outlet 37.

Flow the shell side fluid to and from the shell 10 is by -way of anunderslnng housing 42 attached to the shell exterior in a closingrelation to openings 36 and 37. Housing 42 has an inlet 43 and an outlet44 separated by a partition wall 45. In the latter is a through opening46. A closure member `47 is mounted to one end of the housing `42 andslidably receives the stem of a valve 48 adapted to seat on partition 45in a position closing opening 46. A compression spring 49 urges valve 4Sto a seated position.

Shell side fluid enters the heat exchanger by Way of inlet 43, flowslongitudinally of housing 42 to shell inlet 36. Flowing t-hrough theinterior of shell 10 in the manner described, the shell side fluiddischarges from shell outlet 37 and leaves the heat exchanger by way ofoutlet 44. Valve 48 normally denies by-passing flow between inlet 43 andoutlet 44, compelling the shell side fluid to travel the describedlroute through shell 10. However, in the presence of a pressure dropsufficient to overcome spring 49, valve y48 opens, allowing at least apart of the flowing fluid to pass directly to outlet 44.

The pressure of shell side fluid within the core of the heat exchangerthus is limited to a predetermined high value.

The tube side fluid enters t-he heat exchanger by way of boss 22,collects in chamber 17 and flows through tube 13 to chamber 24, leavingthe heat exchanger by way of openings 35 and bore 33 in closure cap 26.The flow of tube side fluid is controlled by valve -means in the form ofa cylindrical stem 51 cooperative with pad 13 to control flow throughopening 21. The extremity of valve means 51 is blunt and recessed toprovide an annular surface 52 adapted to engage seat 19 on pad 18 with aflush mating contact. The valve means is positioned to be concentric'with opening 21, with surface 52 engaging seat 19 in a surroundingrelation to opening 21 thus closing the opening in a seated position ofthe valve. The cylindrical valve stem 51 projects from one end of acylindrical valve body 53 slidably mounted in a tubular housing 54. Thehousing 54 is received in a longitudinally nested relation to the bundleof tubes 13. It is concentrically disposed with respect to shell 10,within the shell, and has one end received in a central opening 55 inthe header plate 11. The extremity of the tubular housing is flared intosecure engagement with header plate 11, to anchor one end of the tubularhousing. The other end terminates within the shell in spaced relation tothe other header plate 12. Central openings in the baffles 38, 39 and 41receive the housing 54 with a moderately close fit and assist inmaintaining it positioned as illustrated.

Longitudinal sliding motion of the valve body 53 extends and retractsthe outer end of valve means 51 relative to valve seat 19. The valve`body and integral valve stem extension 51 are parts of a control valveassembly further including a power type thermostat 56. The latter is aknown type of device comprising a casing 57 containing a thermallysensitive material having the capability -of expansion with considerableforce when heated. Case 57 is disposed to project from the inner end oftubular housing 54 in a manner to lie across the final pass traversed bythe shell side fluid as it flows to shell outlet 37. The thermostat caseaccordingly is contacted by the shell side fluid under conditions inwhich the thermally sensitive material is exposed to the shell sidefluid at the temperature at which it discharges from the heat exchangercore. The case S7 has a reduced diameter shank portion 58 extending intoa vbushing 59 installed in the tubular housing 54 in a manner to besecure against relative longitudinal motion therein. The reduceddiameter portion 58 terminates in a threaded stud 61 extending throughthe closed `bottom of bushing 59 and having a threaded connectiontherewith. A nut 62 locks the threaded stud 61 to bushing 59. Within thethermostatic power unit and extending longitudinally of reduced shankportion 58 and stud 61 is a plunger 63 extending through and beyond stud61 toward valve body 53. The adjacent end of valve `'body 53 is open toa longitudinally recessed portion in which is a compression spring 64projecting a piston 65 outwardly or rearwardly in the valve body, thismotion being limited by an installed ring 66. Spring 64 urges piston 65outwardly or rearwardly of the valve body 53 while a coil spring 67urges the valve body S3 rearwardly or in a direction to cause piston 65to engage plunger 63 with which it is aligned. The spring 67 is seatedon a limit member 68 held in the tubular housing 54 near its one endwithin header plate 11 by a retainer ring 69.

The plunger 63 extends axially toward valve body 53 in the presence of arising shell side fluid temperature, as sensed `by thermostatic powerunit 56. The plunger acts on piston and through spring 64 moves valvebody 53 axially to advance valve stem means 51 toward pad 18. At apredetermined high shell side fluid temperature the valve means 51 seatson pad 18 and closes off flow of the tube side fluid through opening 21.Should the shell side fluid temperature continue to rise and plunger 63continue to extend, this motion is absorbed in an inward movement ofpiston 65 relative to body 53, compressing spring 64. The valve closingmotion compresses spring 67 and provides a force for return of the valvebody when the shell side fluid temperatures decrease. As suchtemperature reduces from a peak high value, the spring 64 initiallyreturns piston 65 from any overtravel, forcibly retracting plunger 63and recompressing the thermally sensitive material in case 57. As piston65 reaches retainer ring 66 the continued retraction of plunger 63 is afunction of bodily movement of valve body 53 as compelled by expandingspring 67. The described movement of body 53 serves also to retractvalve stem means I51 from seat 18, reestablishing flow of the tube sidefluid through opening 21.

The valve body 53 has external `bearing flanges 71 and 72 by which it isslidably mounted in housing 54. These have respective cutout portions 73and 74. The limit member 68 has similar cutout portions 75. Theconstruction is one to admit tube side fluid to both ends of valve body53. In an open position of valve stem means 51, therefore, the body 53is substantially balanced against the effects of fluid pressure so thatits movements are a function solely of the opposing described spring andthermostatic influences.

The control valve assembly operates to maintain a minimum or maximumtemperature value of the shell side fluid. In one environmental use towhich the device of the illustrative embodiment is adapted, the tubeside fluid is hot air under pressure, as drawn from the compressor of ajet engine while the shell side fluid is fuel en route from a place ofstorage to the engine. The heat exchanger with control valve assemblyfunctions to heat the flowing fuel when heating is necessary to avoidicing conditions. Thus, at low fuel temperatures as for exampletemperatures below 45 F. valve means 51 stands in an open position,allowing hot air t-o enter the heat exchanger through opening 21 and toflow through tubes 13, thereby heating the fuel flowing over and aroundthe tubes. As the temperature of the flowing fuel rises, in response tosuch heating, thermostatic power unit 56 reacts by projecting plunger 63and moving the valve body to close or further to restrict flow of theincoming hot air. The heating effect thus is reduced as required oralternatively is turned on and off as temperature requirements of thefuel may indicate.

Use of a thermostatic power unit 56 as the sensor has practicaladvantages, as for example obviating the need for servomechanisms andthe like. Within the instant inventive concepts, however, thethermostatic power unit could be replaced by bellows or the likeresponding to changes in pressure drop of the shell side fluid or toother changing conditions of the shell side fluid, with intermediatemeans effecting adjustment of a valve means 51. Alternatively, thebushing 59 and mounted thermostat could be replaced by an electricsolenoid suitably controlled to project and retract a plungercorresponding to the plunger 63 to effect bodily movements of a valve`body within housing 54.

In the illustrated embodiment of the invention, heat transfer tubes 13are provided in rows forming an assembly which at its top and bottom isspaced a substantial distance from side walls of the shell 10. Theresult is to provide above and below the tube bundle flow chambers oflow flow resistance. The total pressure drop across the heat exchangerfor the shell side fluid thus is relatively low. Also the shell sidefluid is enabled easily to distribute itself before beginning each passacross the tube bundle for uniform flow through such pass.

As indicated, the internal placement of the control valve assembly lendscompactness to the heat exchanger combination, provides for the sensingof true temperature values and avoids lag or delay in response. Theconstruction lends itself to simplified installation of the controlvalve assembly, as well as access for inspection and replacement. Theexpanded liange 29 seated in and closing a larger center opening inheader plate 12 is integral with end closure cap 26. Removal of this capwithdraws ange 29 and opens thermostatic unit 56 to access. Inassembling the heat exchanger parts thereof are interconnected insubassemblies and brought together. Thus, the header plates 11 and 12,tubes 13 and baffies 38, 39 and 41 define a core which in the presentinstance further includes tubular housing 54 and installed bushing 59.These parts are assembled together and placed in the shell with theresulting assembly being subjected to a brazing operation. Thesubassembly comprising housing 42 and valve 48 is secured as by weldingto the exterior of shell 10. Thermostatic power unit 56 is insertedthrough header plate 12 to seat in bushing 59 with its stud 61projecting therethrough. From the opposite end of the tubular housing,using a suitable tool, jam nut 62 is secured in place. Valve body 53 isinstalled from the same said opposite end of the tubular housing,assuming a position wherein valve means 51 projects through and beyondheader plate 11. Installation of spring 67, limit means 68 and retainerring 69 adjusts the valve body to a position of contact withthermostatic plunger 63. The end caps 15 and 26 are bolted in place torespective rings 14 and 25 which may be secured to the shell 10 as apart of the brazing process. Pad 18 is placed thereby in an adjacentfacing relation to the surface 52 on valve means 51 With the parts beingready for cooperative action as described.

The reduced diameter portion 58 of the thermostatic power unit 56 has`O-ring seals 76 and 77 mounted thereon. Other seals 78 are installed inthe periphery of expanded flange 29. As a result the tube side and shellside iiuids are separated in a manner to preclude mixing.

Mounting of the valve components in a center tube within the coreassembly -has particular utility in an environmental use as presentlydescribed. The thermostatic power unit is protected by contact byexcessive air temperatures as is overtravel spring 64 and to a largeextent compression spring 67 as well. Both springs are out of the mainhot air flow path. The flowing hot air moves with considerable pressureand velocity effects. The support of tubes 13 by baiiies 38, 39 and 41substantially inhibits vibratory action.

The heat exchanger valve combination disclosed is designed for growth.Increased heat transfer performance can be obtained by lengthening thepath of flow of the shell side iiuid over the tubes, through use ofadditional baiiies, within allowable pressure drop specifications. Minormodifications to the modulating air iiow control by increasing the valvediameter seat will increase available air flow. The surface area withinthe tube bundle can be increased a substantial amount with a minimumincrease in allowable fuel pressure drop by adding rows of tubes 13. Allgrowth changes can be made in an existing heat exchanger construction.

Valve surface 52 engages valve seat 19 with a substantially squarecontact inhibiting leakage. By controlling the clearance between theflanges 71 and 72 of the valve body with respect to tubular housing 54,the valve may be made self-adjusting within limits to assure a uniformcontact between surfaces 52 and 19.

As indicated above, the control valve assembly lends itself to otherforms wherein temperature or pressure sensing means, or manuallyactuated means, indirectly effects flow control of the tube side iiuid.An example appears in FIG. 3 wherein a tubular shell 79 mounts headerplates ,81 (one shown) between which are disposed heat transfer tubes82. An end cap 83 closes one end of the shell 79 and defines with theadjacent header plate 81 an intermediate chamber 84. A central openingin cap 83 admits tube side fluid under pressure to chamber 84 to flowlongitudinally through tubes 82. Flow through opening 85 is controlledby a sleeve type valve 86 having a tapered nose portion 87 and acylindrical skirt portion 88, the latter being slidable on a stationaryboss-like projection 89 integral with insert means 91 installed in anend of a tubular housing 9 2 corresponding to the tubular housing 54 ofthe FIG. l embodiment. The housing 92, like housing 54, is fixed to belongitudinally disposed in the tube bundle and to project at one endinto and through a header plate 81. The boss-like projection 89 is openat its end into the housing 92 and is closed at its other end except fora restricted orifice-like opening 93. A needle valve 94 extends fromhousing 92 through header plate 81 into boss-like projection 89 and isadapted to seat in to close orifice opening 93. A spring 95 may beprovided to -urge valve 94 to a closed position While temperature orpres sure sensing means installed in housing 92 within the heatexchanger core are provided to retract the valve to an open position.The tapered nose valve 87 has a reduced diameter opening 96 in itscenter. Radial port means 97 connect the interior of boss-likeprojection 89 to chamber 84.

Operation of a device as illustrated and described will largely beself-evident. Tube side fluid is free to flow through opening 85 throughrestricted passage 96 into a chamber 98 interiorly of valve 87. Withvalve 94 closed pressure in chamber 98 reacts on the outer end ofbosslike projection 89 and urges valve 87 closed, the valve `87presenting a larger surface area to closing pressure than is provided toan opening pressure at opening 85. Upon retraction of valve 94, however,the pressure in cham'ber 98 reduces whereupon the pressure available toforce valve 87 open is effective to open the valve and iiow of the tubeside fluid in volume takes place through opening 85 directly intochamber 84.

What is claimed is:

1. A tubular heat exchanger, including a shell; spaced apart headerplates in said shell; heat transfer tubes extending between said platesand defining a tube bundle, tube side and `shell side fluids iiowing inheat transfer relation respectively through and around said heattransfer tubes, means attaching to said shell in an adjacent spacedrelation to one of said header plates having a tube side iiuid flowlopening in series relation to said tubes, a modulating tube side fluidfiow control valve assembly disposed longitudinally of said shell withinthe tube bundle, including valve means extensible through said oneheader plate and cooperating with said attaching means to control iiowof tube side fluid through said opening therein, a tubular housinglongitudinally nested in said tube bundle and mounting said controlvalve assembly therein, one end of said tubular housing being open andinterengaging with said adjacent header plate to align with an openingtherein through which said valve means projects, said control valveassembly further including a valve body slidable in said tubular housingand means to extend and retract said valve body therein, said attachingmeans including a pad upon which said valve means seats in response toan extending motion of said valve body to close the opening in saidattaching means, the other end of said tubular housing terminatingwithin the tube bundle between said header plates, and la thermostatanchored in to react on the said other end of said tubular housing, saidthermostat having temperature housing sensing means projecting beyondthe tubular housing into the tube bundle to be contacted by the shellside fluide flowing over the heat transfer tubes, -said thermostatfuurther having a plunger projecting into the tubular housing to engagesaid valve body, a rising shell side fluid temperature extending saidplunger correspondingly to extend said valve body.

2. A tubular heat exchanger according to claim 1, characterized byspring means opposing extension of said valve body and operable upon alowering shell side fluid temperature to retract said valve body andsaid plunger.

3. A tubular heat exchanger, including a shell; spaced apart headerplates in said shell; heat transfer tubes extending between said shell;heat transfer tubes extending between said plates and defining a tubebundle, tube side and shell side fluids flowing in heat transferrelation respectively through and around said heat transfer tubes, meansattaching to said shell in an adjacent spaced relation to one of saidheader plates having a tube side fluid flow opening in series relationto said tubes, a modulating tube side fluid flow control valve assemblydisposed longitudinally of `said shell within the tube bundle, includingvalve means extensible through said one header plate and cooperatingwith said attaching means to control flow of tube side fluid throughsaid opening therein, said attaching means having the form of a pad,said valve means being extensible to seat on said pad to close theopening in said attaching means and retractable to allow flow throughsaid opening, and a tubular housing longitudinally nested in said tubebundle and having an open end received in said adjacent header plate tocommunicate therethrough with the space between said adjacent headerplate and said attaching means, the control valve assembly being mountedin said housing and further including a thermostat installed in toproject from the opposite end of said tubular housing to sense thetemperature of the shell side fluid, and said control valve assemblystill further including a valve body slidable in said housing andterminating at one end in said valve means, a yielding connection beinginterposed between said thermostat and said valve body accommodatingovertravel of said thermostat after seating of said valve means on saidpad.

4. A tubular heat exchanger according to claim 3, characterized by meansfor substantially balancing said valve body endwise in said housingagainst the effects of tube side fluid pressure.

5. A tubular heat exchanger, including a shell and a cap closing one endof said shell and having a tube side fluid flow opening therein, spacedapart header plates in said shell, said shell having spaced apartopenings between said header plates for in-llow and out-flow of a shellside fluid, a tubular housing longitudinally disposed in said shell andspaced from the walls thereof, a control valve assembly mounted in saidtubular housing and extensible through one of said header plates tocontrol flow of the tube side fluid through said closing gap, and heattransfer tubes in said shell extending between and interconnecting saidheader plates, said tubes being arranged in multiple transverse rowssubstantially to surround said tube housing, said control valve assemblyincluding a rst valve adapted to seat on said cap to close said openingtherein against the pressure of tube side fluid and providing aninterior chamber in which tube side fluid is admitted to maintain saidfirst valve normally closed and said valve assembly further including asecond valve extensible from within the tubular housing to deny andpermit escape of fluid from said interior chamber.

6. A tubular heat exchanger, including a shell and a cap closing one endof said shell and having a tube side fluid flow opening therein, spacedapart header plates in said shell, said shell having spaced apartopenings between said header plates 'for in-flow and out-flow of a shellside fluid, heat transfer tubes in said shell extending between andinterconnecting said header plates, said tubes for-ming a tube bundle,means constraining the shell side fluid to flow over the tube bundle ina plurality of passes, a tubular housing longitudinally disposed in saidshell nested within the tube bundle, a control valve mounted in saidtubular housing and extensible through one of said header plates tocontrol flow of the tube side fluid, and thermostatic means disposedbetween said header plates in said tube bundle in the path of llow ofthe shell side fluid as it flows through one of said passes to operatesaid valve.

7. A tubular heat exchanger according to claim 6, characterized in thatsaid control valve includes a first valve movable against the pressureof incoming tube side fluid to close flow through the opening in saidcap and providing an interior chamber in which tube side uid is admittedto maintain said first valve normally closed and said control valvefurther including a second valve extensible from within the tubularhousing to deny and permit escape of fluid from said interior chamber.

8. A tubular heat exchanger according to claim 6, characterized in thatsaid thermostatic means is anchored in to react on said tubular housing,said housing being formed freely to expose said thermally sensitive endto the flowing shell side fluid.

9. A tubular heat exchanger according to claim 8, characterized in thatsaid thermostatic means is positioned to dispose the thermally sensitiveand thereof opposite the out-flow opening in said shell in the final oneof said plurality of passes.

References Cited UNITED STATES PATENTS 1,344,423 6/1920 Manker 236--191,881,771 10/1932 Lyman 236-93 3,109,589 11/1963 Kimm 165-39 XR3,145,928 8/1964 Parker et al. 165-158 XR 3,353,590 11/1967 Holman165--158 XR ROBERT A. OLEARY, Primary Examiner.

MANUEL A. ANTONAKAS, Assistant Examiner.

U.S. Cl. X.R. 23 6-019

